1. Field of the Invention
The present invention relates to a method of manufacturing a semiconductor device by bonding metal posts of a mother chip and metal posts of a daughter chip to each other by means of solder film in a thermocompression bonding manner and, more particularly, to a semiconductor device manufacturing method which enables prevention of the occurrence of imperfect contact between a mother chip and a daughter chip.
2. Background Art
In recent years, semiconductor devices having a chip-on-chip (COC) structure in which a daughter chip is flip-chip-connected to a mother chip and having the mother chip flip-chip-connected to a circuit substrate have been proposed. In flip-chip connection between the mother chip and the daughter chip, metal posts of the two chips are bonded to each other in a thermocompression bonding manner by means of solder film. The proposed semiconductor devices include ones in which solder film is formed on the surfaces of each of the group of metal posts on a mother chip and the group of metal posts on a daughter chip (see, for example, Japanese Patent Laid-Open Nos. 2004-79685 and 2004-146728) and ones in which Au film is formed on one of the groups of metal posts on a mother chip and a daughter chip, while solder film is formed on the other group of metal posts (see, for example, Japanese Patent Laid-Open Nos. 2002-164498 and 2003-133508).
In the case of forming solder film on metal posts on a mother chip, thereafter forming solder balls having a large diameter on peripheral electrodes on the mother chip, and bonding the metal posts on the mother chip and metal posts on a daughter chip to each other in a thermocompression bonding manner by means of the solder film, thick oxide film having a thickness of 10 to 20 nm is formed in the surface of the solder film exposed on each metal post in regions where no solder balls are formed, by ref lowing for forming the solder balls. Therefore, there is a problem that, at the time of flip-chip connection of the daughter chip to the mother chip, the thick oxide film in the surface of the solder film cannot be broken and failure of connection between the mother chip and the daughter chip occurs.